Extremum seeking control with actuator saturation control

• US 8,200,345 B2
• Filed: 01/07/2010
• Issued: 06/12/2012
• Est. Priority Date: 07/17/2007
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Li, Yaoyu, Seem, John E.
• Primary Examiner(s): Decady, Albert
• Assistant Examiner(s): LEE, DOUGLAS S
• Application Number:
  US12/683,883
• Publication Number:
  US 20100106331A1
• Time in Patent Office: 887 Days
• Field of Search: 700/28, 700 30- 34, 700/276, 700299-300, 714/37, 714/39
• US Class Current: 700/38
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2011/0006 using low temperature external supply air to assist cooling
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 5/01 electric

Abstract

An extremum seeking control method optimizes a control process for a plant such as an air handling unit. The method improves the performance of an extremum seeking control strategy by limiting, removing or preventing the effects of an actuator saturation condition, particularly as the extremum seeking control strategy relates to HVAC applications.

Claims

1. A method for optimizing a control process for an actuator, the method comprising:

operating the control process using an extremum seeking controller;

using an electronics circuit to compensate for an actuator saturation condition of the extremum seeking controller, wherein the step of compensating for an actuator saturation condition comprises;

receiving a feedback signal from the actuator;

subtracting the control signal provided to the actuator from the feedback signal to obtain a difference signal;

amplifying the difference signal to exaggerate the difference signal; and

adding the amplified difference signal to an input of an integrator of the extremum seeking controller to limit the input to the integrator.

4. The method of claim 1, wherein the actuator is an actuator for a damper in a heating or cooling system and wherein the extremum seeking controller is configured to regulate temperature of air in a building space using the actuator.

2. A controller for controlling an actuator, the controller comprising:

a processing circuit configured to operate the plant using an extremum seeking control module and to compensate for an actuator saturation condition of the extremum seeking control module;

an input configured to receive a feedback signal from the actuator; and

an output configured to send a control signal to the actuator;

wherein the processing circuit is configured to subtract the control signal from the feedback signal to obtain a difference signal and wherein the processing circuit is further configured to amplify the difference signal to exaggerate the difference signal and to add the amplified difference signal to an input of an integrator of the extremum seeking control module to limit the input to the integrator.

5. The controller of claim 2, wherein the extremum seeking control module is configured to regulate the temperature of air in a building space by adjusting the position of the actuator.

3. A controller for an air handling unit having an actuator that opens and closes a damper to control the amount of outdoor air used for cooling the air provided to a building space by the air handling unit, comprising:

an input interface configured to receive a temperature sensor input;

a temperature regulator control module configured to provide a command to a temperature regulator system configured to chill air provided by the air handling unit, wherein the temperature regulator control module determines the command based on the temperature sensor input received at the input interface;

an extremum seeking control module configured to receive the command from the temperature regulator control module and comprising an integrator and a performance gradient probe, the performance gradient probe configured to use the received command to detect a difference between an estimated optimal position for the actuator and a current actuator position and to provide the detected difference to the integrator, wherein the integrator is configured to calculate an actuator command signal configured to reduce the detected difference;

an output interface configured to provide the actuator command signal to the actuator; and

a feedback interface configured to receive a feedback signal from the actuator representative of the actual position of the actuator after the actuator is adjusted in response to the actuator command signal;

wherein the extremum seeking control module is further configured to determine an error between the actuator command signal and the feedback signal;

wherein the extremum seeking control module is further configured to add the error to the detected difference provided to the integrator of the extremum seeking control module;

wherein the addition of the error to the detected difference of the integrator is configured to reduce or change the sign of the detected difference provided to the integrator;

wherein the estimated optimal position for the actuator is calculated to minimize the power consumption of the temperature regulator system by maximizing the use of outdoor air provided to the building by the damper;

wherein the extremum seeking control module comprises a first processing element configured to determine the error between the actuator command signal and the feedback signal by subtracting the actuator command signal from the feedback signal, wherein the extremum seeking control module further comprises a second processing element configured to amplify the error by a gain to at least offset integrator windup, and wherein the detected difference provided to the integrator of the extremum seeking control module is not affected by the second processing element when the error is zero.